Since　the　effect　of　intermediate　principal　stress　on　the　strength　of　pavement　materials　is　not　entirely　clear　so　far,　a　proprietary　true　triaxial　apparatus　was　developed　to　simulate　the　spatial　status　of　principal　stresses　to　conduct　compressive　strength　tests　on　different　gradations　of　AC-13,　different　cement　contents　of　cement-stabilized　macadam.　With　the　same　minimum　principal　stress,　the　triaxial　compressive　strengths　of　cube　specimens　under　different　intermediate　principal　stresses　were　compared.　The　results　indicate　that,　as　the　intermediate　principal　stress　increases,　the　compressive　strength　of　the　specimen　increases　and　then　decreases;　different　gradations　of　AC-13　do　not　show　much　difference　in　triaxial　compressive　strength　while　different　cement　contents　of　cement-stabilized　macadam　indicate　considerable　difference.　Analysis　results　suggest　significant　effect　of　intermediate　principal　stress　on　the　compressive　strength　of　pavement　materials:　for　AC-13,　the　coarser　the　gradation,　the　greater　the　effect　of　intermediate　principal　strength　on　its　strength;　for　cement-stabilized　Macadam,　the　higher　the　cement　content,　the　greater　the　effect　of　intermediate　principal　stress.　Strength　model　analysis　results　suggest　that　Double-Shear-Corner　Model　is　more　suitable　to　characterize　cement-stabilized　macadam＇s　strength　performance　compared　to　the　Mohr-Coulomb　model　and　Double-Shear　Model.　©　2018　by　the　authors.